1) Field of the Invention
The present invention relates to a technology for identifying a servo track writer (STW) device used for servo track writing on a disk.
2) Description of the Related Art
The disks of magnetic disk devices are subjected to servo track writing prior to shipping. “Structure and Practical Applications of Hard Disk Device—Principles and Mechanism of Recording/Reproduction & Interface”, published in CQ, issue no. ISBN4-7879-3622-4, P90-93 by Hiroshi Okamura discloses servo track writing. The servo track writing is a process by which head position information, servo information, etc. (hereinafter, “STW information”) are recorded on the disk and is carried out by a dedicated device (hereinafter “STW device”).
FIG. 6A and FIG. 6B are schematics for explaining the servo track writing. The STW device records the STW information on a magnetic disk with the aid of the magnetic head, and, with the aid of a magnet, transfers the STW information to other magnetic disks from a master medium already having the STW information recorded thereon.
Thus, by using the STW device for servo track writing, the magnetic disk device accomplishes the task of servo track writing more precisely than would be the case if the magnetic disk device itself were to carry out servo track writing. Consequently, defects in the magnetic disk device can be forestalled.
Further, a bar code is affixed to a post-shipment magnetic disk device to make it possible to identify the STW device that was used for servo track writing on the disk. Thus, in case of any malfunctioning of the magnetic disk device, the bar code can be used to identify the defective STW device.
However, conventional technology does not always assure correct identification of the defective STW device.
The reason for this is that the bar code affixed to the magnetic disk device is easily damaged during handling, causing it come off or become worn. Consequently, the information recorded on the bar code cannot be read properly. Further, since the bar code is merely affixed to the magnetic disk device, any unauthorized person may tamper with the bar code information, leading to security breach.
This problem may be countered by recording on the disk an identification information of the STW device. However, since formatting the magnetic disk device erases the identification information, this method is not an appropriate solution.